He manipulates her all over chapters four, five, and six in order to get the more expensive chest the moke skin bag, as well as the healer's kit.

As for the blackmail, from chapter six:

Justice and reason will both fail. You must either find something you have that she wants, or find something you can do which she fears...

Ah.
"Well then, Professor," Harry said in a low, icy tone, "it sounds like I have something you want. You can, if you like, tell me the truth, the whole truth, and in return I will keep your secrets. Or you can try to keep me ignorant so you can use me as a pawn, in which case I will owe you nothing."

McGonagall stopped short in the street. Her eyes blazed and her voice descended into an outright hiss. "How dare you!"

Thank you for clarifying that for me. It was the refusal that mattered, and I can see how that would lead someone down a path seeking normalcy (whatever the hell that is) and shunning everything she sees as abnormal. However, I still don't quite like everything being cleanly changed by that one event, so I think the turn left scenario may still stand.

They're very similar, I suppose that I would say the difference is that persuasion is mostly about changing someone's point of view, whereas manipulation is about emotionally forcing someone to do something. There's something about intent, there, too. Manipulation is, shall we say, darker than persuasion, less honest.

Take the case of the kit, he started out by overblowing his fears and actually making the girl working in the shop run out of the room in tears with a flippant comment (about a friend dying in his arms because he didn't have a med kit or something like that). That's clear manipulation. He only got the kit, though, when McGonagall realized that the actually was afraid, though for different reasons than he had said. Harry was even surprised when she let him get it. That reads to persuasion.

I'm going to summarize here, rather than go search for actual quotes. With the trunk, he promised that he would bring tons of books and donate them to the school after he's finished with them. With the bag, it was along the lines of being able to easily carry all of his textbooks with him. And he so thoroughly convinced her that he was afraid of attack in order to get the healers kit that she thought he had been abused.

I would argue that Harry changed his behavior in order to manipulate her into giving him what he wanted, rather like how Duddly did in canon.

I would imagine that there is a far simplified version used for quick writing. What we do is akin to extremely elaborate calligraphy, whereas there may be something far closer to our print writing that they can use for quick notes, without all of the elaboration. Maybe with short lines only crossing the circle in question (like on a t) rather than full lines.

Only if she were directly copying the disney film. Her painting was obviously off of the description in the book rather than the Disney Movie. Disney doesn't own the rights to the book, just to the movie, so they are definitely still at fault.

They're having him disguise himself through acting, rather than costume and makeup. In TGG, when he was talking to the wife of the man who had faked his death (I can't remember their names) he was acting in a way that was nothing like the Sherlock we know and love. He did that to fool her into telling him what he needed to know. Rather than being the master of disguise described in canon, he's a chameleon, able to blend and morph himself into what he needs to be